A German passenger has been hailed a hero after taking over the controls of a plane and helping it land at Dublin airport.

Details have emerged of how the off-duty pilot offered to help the flight crew after the first officer of the Lufthansa Boeing 747 became ill while flying over the Atlantic on Monday.

When the cabin crew announced the plane was being diverted, the passenger asked why and then offered to help, pointing out he was a qualified pilot.

The German national helped bring the plane down safely in an emergency landing at the airport in the Irish capital shortly before 6am.

Ireland's Air Accident Investigations Unit is examining the incident.

A Lufthansa spokeswoman said the man who stepped in was fully licensed to operate and fly the 747. "In such circumstances it's absolutely normal procedure for the pilot, the flight captain, to continue to operate the aircraft," she said. "Also, where necessary, the cabin crew are fully trained and can be called upon to read checklists back to the pilot. The procedures are in place for such an eventuality. "